Converter



Nov. 11`, ISZ

CONVERTER Filed April 14, 1949 H. AESCHLIMANN 2 SHEETS- SHEET 1 Nov. l1, 1952 H. AESCHLIMANN 2,517,975

CONVERTER Filed April 14, 1949 Y 2 SHEETS--SHEET 2 14o/3" 14e 14s 147 145 Patented Nov. 11, 1952 CONVERTER Hans Aeschlimann, Geneva, Switzerland, assigner to Societe Anonyme des Ateliers de Secheron, Geneva, Switzerland, a corporation of Switzerland Application April 14, 1949, Serial No. 87,460 In Switzerland April 16, 1948 9 Claims. 1

I-litherto the construction of converters has been based on the following principles.

l. The use of solid contacts which are periodically pressed against each other and removed from each other. These converters with solid contacts present several drawbacks, viz.:

(a) Synchronism must be very accurate to avoid the contacts of two adjacent phases 'iron being opened simultaneously;

(b) Special means (inductances) are required or effecting commutation in order to avoid return currents and the formation of arcs;

(c) The electrodes wear out quickly unless iniportant and relatively costly inductance coils are used as commutation means.

2. The use of a mercury vapor arc in a vacuum. In this case the voltage drop in the arc is practically constant and equal to approximately 20 volts. This means that when operating at low voltages the losses are relatively high.

3. The use of a jet of mercury movable in respect to a solid electrode with which it comes in contact periodically. In this case an appreciable amount of power is consumed by the circulation of the mercury for producing the jet.

The present invention aims at avoiding` these drawbacks presented by the comniutators already known and at providing a converter capable to operate under the best conditions both for low voltages and power and for high voltages and power. 1 l

The present invention provides a converter oi the type comprising at least one contact which opens and closes synchronously with the ircquency of the network, characterized in that it comprises at least one container containing mercury and at least one solid electrode, which container rotates plane'tarily on axis which is movable round a fixed axis in order to communicate to the mercury a relative motion with regard to the said solid electrode, and in that the mercury constitutes the cathode for the whole dura tion of each passage or" the current, the commutation ta'king place on the opening oi the circuit in the arc formed between the said cathode and the opposite electrode.

It is evident that with such an arrange;1 ent the drawbacks ci converters with solid electrodes and those relating to mercury vapor converters may be avoided. Moreover, the power required to Icommunicate to the mercury a relative motion with regard to the solid electrode is negligible, with the result that the drawback mentioned above in connection with mercury jet converters is also avoided.

In the converter according to the invention, the commutation takes place in the are, which ohviates, without any special appliance, the drawbacks mentioned in connection with solid contact converters. Furthermore, it will be noticed that the negative characteristic of the arc (increasing resistance as the voltage is reduced) ensures automatic extinction of the arc used for commutation.

The accompanying drawing illustrates by way of example two embodiments of the converter according to the invention.

Fig. 1 is an axial longitudinal section of the iirst embodiment.

Fig. 2 is a cross-section along the line Iii- 1l in Fig. 1;

Fig. 3 is a cross-section along the line lil-lli in Fig. 1;

Fig. 4 is a connection diagrahm of this First embodiment;

Fig. 5 is a View of a detail of a variant;

Fig. 6 is a cross-section of the second embodiment;

Figs. 7 and 8 are views of the details of this second embodiment.

The converter illustrated comprises a cylindrical metallic envelope l to whose ends are xed by means of bolts two bottoms 2 and 3. A shaft 4 which turns in the direction indicated by the arrow 5 passes axially through the center of the bottom 3. The opposite bottom 2 is axially crossed by a shaft 6 arranged precisely in line with the shaft li. The latter is affixed with a disk 'l in which two ball bearings t and 9 are fitted at the same distance from the geometrie axis of the shaft 4 and in diametrically opposite position. Through the ball bearings S and 5 pass two tubes l0 and H, respectively, parallel to shaft 4 round whose axis they rotate together with the disk 1. In order to give the whole arrangement the required rigidity, there is a sec-- ond disk l2 parallel to the rst disk l and carrying two ball bearings I3 and lli through which the tubes l! and il, respectively, also pass.

The tube IB is welded to a small disk i5 to which is attached by means oi the screws a cog I7 which is always in mesh with a crown wheel i3 with internal gearing. The tube ii is welded to a small disk i9 to which is attache-:l in like manner by means of the screws 2d a cog 2i which is always in mesh with a crown wheel 22 with interior gearing. The two crown wheels it and 22 have the same size and are placed side by side. Their external spiral gearings and 24, respectively, engage with the screws 25 and 26, respectively, which screws are arranged in an embossment 2'I of the envelope I in such a way that they rotate without any axial displacement. At one end of these screws, as indicated in 2S for the screw 25, there is a square head by means of which the screws can be turned round their own axes with the help of an adjusting Spanner. By turning the screws 25 and 2S the crown wheels I8 and 22 can be made to rotate round the axis of the converter.

The shaft 6 is rmly attached to a disk 29 parallel to and of the same size as the disk '5. Inside the disk 29 there are two ball bearings 35 and 3i through which pass two tubes 32 and 33, respectively, placed exactly in line with the tubes I and II, respectively, mentioned above. The disks I and 29 are rigidly connected by means of two rods 34 and 35 parallel to the axis of the converter and fixed at their ends to the two afore-mentioned Edisks. It is obvious from the drawing that the rods 34 and 35 are arranged in a radial plane with respect to the axis of the converter, which axis is perpendicular to the radial plane which contains the axis of the tubes I5 and 32 on one side and I I and 33 on the other. The rods 35 and 35 ensure of course the rigid connection not only between the disks 'i and 23, but also between them and the disk I2.

The tube I is also welded to a small disk 33 similar to the disk I5, to which is attached by means of the screws 31 a part 38 Vmade of insulating material whose purpose will be indicated later. In like manner, the tube II is welded to a small metallic disk 39 similar to the disk I5, to

which is attached by means of screws l5 a part 5I made of insulating material and identical with the part 38 just mentioned.

The tube 32, coaxial with the tube l5, is also welded to a small metallic disk I2 to which is attached by means of the screws 43 a part Ill made of insulating material which is placed exactly opposite the part 38 but a certain distance away. Finally, the tube 33, coaxial with the tube II, is

welded to a small disk 45 to which is attached by means of the screws 5 a part M made of insulating material which is exactly opposite the part 4I but a certain distance away.

Inside the cylindrical envelope I there is a cylindrical lining 48 made of insulating material. Inside the insulating lining d8 there are four identical metal rings IIS, 53, 5I and 52 placed a certain distance ap-art and insulated from each other by the insulating rings 53, 53, and 55, respectively. A similar insulating ring 5S is placed between the metal ring 52 and the adjacent crown wheel 22. Each of the conducting rings 39, 50, 5I and 52 is attached to one of the electric terminals 51, 58, 59 and 6I), respectively, which pass through the envelope I and the insulatingY lining 48 and are screwed into their respective rings. An insulating sleeve 5I surrounds each of the said terminals in order to insulate it from the envelope I.

The inner cylindrical surface of each of the rings 59, 50, 5I and 52 constitutes a roller track for a roller that will now be described. The roller which rolls inside the ring 52 is shown at 62 and is arranged so as to be constantly coaxial with the tubes I0 and 32. It is angularly rmly attached to the insulating part 38 by means of three pins 64 whose free ends engage in cavities in the said part 38. This end of each pin 5d is surrounded by a sleeve 65 made of an elastic material such as rubber designed to permit a slight angular displacement of the pins 5l?, relatively to the axis of the tube III in order to ensure that the roller 62 is always pressed rmly against the track arranged in the ring 52. The roller 52 is keyed on to a small shaft 35 coaxial with the tubes Iii and 32.

The roller which rolls inside the ring 55' is shown at '5l' and is angularly firmly attached to the insulating part QI by means of three pins 53 whose free ends engage in cavities in the said part These ends are fitted with a packing 35 made of an elastic material such as rubber in order to allow the pins (58, if necessary, a slight inclination in respect to the axis of the tube l I in order to ensure that the roller @I is always pressed rmly against the track arranged in the ring 5i. This roller 5'? is keyed on to a small shaft 'id coaxial with the tubes I I and 33.

The roller which rolls inside the ring 53 formed by an annular projection 'II on a metal drum 'i2 that constitutes the side wall of a container I3 which holds a certain amount of mercury il. The said container 'I3 is closed at each end by the metal bottoms "i5 and T. Through the bottom I5 passes the small shaft 53 whose free end is prolonged inside the container i3. Two rings 'I'I and 'I8 made of insulating material ensure a tight joint between the shaft 53 and the bottom 'I3 and at the same time a rigid connection between the container I3 and the shaft The connection between the bottom 'I5 of the container 'i3 and the insulating part is similar to that between the roller 62 and the insulating part 33. Three pins 'I5 are rmly xed to the said bottom 'I5 and their free ends engage in cavities in the insulating part M, a packing 823 made of an elastic material such as rubber being fitted round the said end of each pin to allow the said pins, if necessary, a slight inclination in respect to the axis of the tube 52 in order to ensure that the roller 'II is always firmly pressed against the track arranged in the ring 55.

The bottom l5 is also traversed axially by a small tube 8| closed by a screw 32 which functions as a plug. This small tube Si is used for introducing'the mercury 'Minto the container rihe small shaft 'i0 supports a container 83 identical with the container 13. The roller that rolls inside the ring 59 is constituted by an annular projection on a cylindrical piece 35 that forms the side wall of the container 83. The said ccntainer 83 is closed at one of its ends by a bottom 35 identical with the bottom 'It and at the other end by a bottom 8l identical with the bottom l5. Insulating rings 88 and 89 identical with the rings Ti and i5 ensure a tight joint between the shaft il and the bottom 85 and a rigid connection between the said shaft and the said bottom. Mercury 93 is placed in the container 83. A small tube SI that passes axially through the bottom 87 is used to introduce the mercury. This tube is closed by a screw 92 which functions as a plug.

The bottom 8'1 of the container 83 is attached to the insulating part 41 by means of three pins 93 firmly xed to the said bottom and whose free ends engage in cavities in the said part lI'I. In this case also the said end of each pin is surrounded by a packing 94 made of elastic material such as rubber to allow the pins 53, if necessary, a slight inclination in respect to the axis of the tube 33 in order to ensure that the roller 55 is always rmly pressed against the track arranged in the ring 43.

On the free end of the shaft 65, which, as we have seen, is prolonged inside the container I3, there is a number of metal ns 55 which extend radially to the proximity of the cylindrical Wall l2. These fins which have all the same profile, illustrated in Fig. 2, viz. a segment of a circle of small aperture, are keyed on to the shaft 66. The number of the fins depends on the intensity of the current to be allowed to pass through the converter. In fact, as will be seen later, these fins constitute one of the two electrodes (the other being constituted by the mercury 14) between which the opening and closing of the circuit is eifected.

In like manner the fins 96, identical with the iins 95, are keyed on to the shaft 'I0 and constitute one of the two electrodes (the other being constituted by the mercury 90) between which the opening and closing of the circuit is effected.

The converter described above operates in the following manner:

When the shaft 4 rotates in the direction of the arrow 5 the axis of the containers 'I3 and 33 are driven with it at the same angular speed. Consequently, the axes of the said containers revolve round the fixed axis of the converter. Moreover, the rotation of the shaft 4 causes the cogs Il and 2l to revolve on the interior gearing of the crown wheels I8 and 22, respectively. The diameter of the said cogs is exactly half that of the gearing of the said crown wheels. The diameter of the four cylindrical tracks in the rings G9, 50, 5I and 52 is equal to that of the gearings of the crown wheels I8 and 22. Furthermore, the diameter of the four rollers 62, 61, 'Il and 813 is equal to that of the cogs I1 and 2 I. Consequently, the rollers 62, B1, H and 34 roll without sliding on their respective tracks causing the containers 'I3 and 83 to rotate round their own axes while the said axes revolve round the main axis of the converter.

The centrifugal force due to the motion of the containers round the xed axis of the converter drives the mercury as far as possible from the said axis so that it takes up the position indicated in Fig. 2, where in each of the containers 'i3 and 83 its free surface assumes the shape of part of a cylinder whose axis is the axis of the converter. The rotation of the containers round their own axes causes the shafts 66 and 1B to rotate round their own axes in the direction contrary to that of the shaft 4.

In Fig. 2 the arrow 91 indicates the direction in which the disk 29 rotates, i. e. the shaft d, and the arrows S3 and 99 indicate the directions in which rotate the shafts 66 and lil and their fins 95 and S6, respectively. It follows that the conducting ns 95 and Sii are introduced periodically into the mercury and periodically withdrawn from it. The velocity of rotation of the shaft 4 is selected in such a way in relation to the frequency of the network that the formation cf the contact between the fins and the mercury and the breaking of the said contact are synchronized with that frequency. If, for instance, the converter is to be employed as a rectifier in a monophase circuit, the connections are arranged as indicated schematically in Fig. 4. The secondary winding IB@ of the feed transformer has a median pole IGI. One end of the secondary winding I is connected with the terminal 51 and the other end with the terminal 53. The terminals 59 and @il are connected with a common point |82. The circuit |63 of the current rectied by the converter is arranged between the points ESI and IEI2. It could be seen that during one semi-period one of the containers '13, 63 functions as rectifier while the other is idle, and during the other semi-period the reverse is true. Therefore the current enters at the terminal 58 and passes successively through the ring 5U, the roller 'Il and the metal wall 'l2 of the container 'I3 till it reaches the mercury 14. At the instant under consideration the metal fins dip into the mercury. Consequently the current passes successively from the mercury through the said fins, the shaft 66, the roller 62 and the ring 52 to the output terminal 60. During that time no current circulates between the terminals 51 and 59 since the ns 96 are out of contact with the mercury 90.

The arrangement is provided in such a way that the mercury forms the cathode for the whole time the current passes through one of the containers. Under those conditions the commutation takes place, on the opening of the circuit between the respective fins and the mercury, in the arc that is formed between the mercury cathode and the opposite electrode, i. e. the solid metal fins.

In the example described above the solid electrode constituted by the ns 95, respectively 9E, acts as anode during the whole passage of the current. In the variant according to Fig. 5 the said solid electrode acts as anode for the major part of the time the current passes through the respective container. In this case, in each of the fins, for instance 95, at the part that leaves the mercury I4 on the opening of the circuit, there is a funnel-shaped cavity [G4 open at each end. This cavity is designed in such a way that it is filled with mercury when it dips into the mass of mercury 14 and that the arc which effects the commutation is formed between the drop of mercury |05 that appears at the small end of the cavity |04 and the surface of the mercury 1d. Simultaneously with the commutation and the extinction of the arc the small quantity of mercury contained in the cavity |84 escapes therefrom under the action of the centrifugal force. In this variant the arc is formed during the brief instant of commutation between the mercury 'i4 that acts as cathode and the drop of mercury |55 temporarily lodged in the fin 95. Consequently, during that brief instant the said drop of mercury acts as anode.

It will be noticed that in the embodiment described above the current is fed to the electrodes without using sliding contacts or flexible conductors. In this way wearing out of the leading contacts and breaking through fatigue of the flexible conductors employed in many of the known devices are avoided. Here, as already seen, the current is fed by means of rollers which roll practically without any slip on a xed metal track, so that practically no wear occurs. Good Contact between the said rollers and their respective tracks is ensured by the fact that the rollers are pressed firmly against the tracks by the centrifugal force.

It should likewise be noted that the instant of commutation in each of the containers can be adjusted at will by mechanical means even while the converter is in operation. In fact, the adjusting screws 25 and 25 enable the angular position of each container in respect to its own axis to be adjusted without any displacement of this axis around the main axis of the converter. Finally, it will be noted that as a result of the movement of the containers round the fixed axis the mercury is subjected to a centrifugal force which is amply suiiicient to stabilize the surface of the said mercury at the point where commutation takes place, and to obviate any parasite 7 oscillations thatl might disturb the precision (in respect ofV time) of' the said commutation.

The second embodiment illustrated in Figs. 6 8, comprises a casing H1B-in which rotate two shafts |01 and |08 arranged exactly in line with each other and rmly attached to a rectangular frame |091. The shaft |01 is attached to a driving pulley H which communicates a rotatory movement to the frame |09. Three contact rings ||2 and |3I are keyed or shrunk on to the shaft |08 and are electrically insulated' from each other. With each of these rings cooperate one of the brushes H4, H5 and H5, respectively, carried by the brush-holders H8 and H9, respectively, which are supported by an arm |20. firmly attached to the casing |06'.

Through the center ofthe frame |09 passes a shaft |2| perpendicular to the common axis of the shafts |01 and |08. The shaft |2| carries a conical cog |22 which meshes with the xed conical geared crown wheel |26 arranged inside the casing |06. The shaft |2| also carries three rings |23", |24 and |25 electrically insulated from each other. With each of these rings cooperates one of the pairs of brushes |21, |28 and |29-, respectively, carried by the pairs of brush-holders |30, |3| and` |32, respectively, which are supported in turn by two arms |33 and |34 attached to the frame |09 and extending parallel to the shaft I2 Finally, on that part. of the said shaft |2| which lies inside the frame |09 is keyed or shrunk a wheel |35 on whose rim. is arranged a tore-shaped container |36. The part of the container |36 shown in cross-section in Fig. 6 is reproduced on a larger scale in Fig. 7, where |31 is the disk of' the wheel |35 and |30' its rim. Around this rim are fitted two rings |39 and 40 made of insulating material. These rings are kept apart by an insulating ring |4| which is disposed between them at their portion which is further away from the shaft I2 A metal ring |42 having a radial flange |43 embraces the rings |39, |40 and |4I. An annular p-late .|44 screwed to the side of the rim |38 and to the side of the ring |42 opposite the ange |43 keeps the unit formed by the rings |39, |40, |4| and |42 in place on the rim |38. The rings |39, |40, |4| and |42, in conjunction with the rim |38, form an annular chamber |45 of rectangular cross-section in which there is a certain amount of mercury (not shown in the drawing).

In the sides of the insulating rings |39` and |40 that face each other annular cavities 46 and |41, respectively, are cut. These two cavities are exactly opposite each other. In the cavity |46 is arranged a metalv ring |48, shown in crosssection in Fig. '1; in the cavity |41 is arranged a ring, such as shown in the plane view of Fig. 8. This ring is divided into two metal parts |49 and |50, each of which occupies slightly less than half its circumference and two intermediate insulating parts |5| and |52 designed to insulate the two conducting parts |49 and |50 from each other. In Fig. '1 one of the conducting parts |49 is shown in cross-section.

Let us suppose that the converter illustrated in Figs. 6-8 is used for supplying an apparatus with rectified current. In this case the secondary winding of the feed transformer has a median pole connected with one of the terminals of the apparatus. One of the two ends of the said secondary Winding is connected with the brush I4, the other with the brush I6. The brush l5 is connected with the other terminal of the apparatus. The following connections inside the con- 8 verter are indicatedv diagrammatically by dotted lines:

The ring is connected electrically with the pair of brushes |21; the ring |'2 with the pair of brushes |28; and the ring ||3 with the pair of brushes. |20. The ring |23 is connected with the half ring |49; the ring |24 with the complete ring |48', and. the ring |25 with the other half ring |501 The converter operates as follows:

When the pulley l0 revolves it communicates to the container |36 a rapid rotation round the axis of the shaft 2| and at the same time a motion due to the rotation of the said shaft |2| roundv the common fixed axis of the shafts |01 and |08. The first mentioned rotation strains the mercury in the annular chamber to occupy constantly the periphery of the said chamber. The second motion, which is synchronous with the frequency of the network, causes the mass of mercury inA the annular chamber |45 to move insidevthesaid chamber at a speed synchronous with the frequency. Consequently, the said mass of mercury is constantly in contact with the metal ring |48 and alternatively in contact with the half rings |44 and |50. Therefore it forms an electric connection between the half ring |40, respectively |50, which it contactsy and the complete ring |43. CommutationA takes place at the instant the mass of mercury reaches one of the insulating zones |'5| or |52 between the half rings |49' and |50. The connections are established in such a way that the mercury always acts as cathode, the anode being alternately the solid metal parts |49 and |50. As in the first embodiment, communtation takes place in the arc formed between the mercury cathode and the solid metal anodes |40 and |50.

What I claim is:

1. A converter having at least one contact which opensand closes periodically and comprising a rotatable main shaft, at least one container having mercury therein, means mounting said container on said shaft for rotation about an axis which is eccentric relative to the axis of rotation of said mainshaft and moves about the latter as said mainshaft rotates, driving means for rotating said main shaft and for rotating said container about said eccentric axis so that the mercury in said container is centrifugally urged against the periphery of the container by the rotation of the latter about said eccentric axis and radially outwardly relative to the axis of said main shaft by the movement of said eccentric axis about the axis of the main shaft to thereby collectv the mercury in at least one location in said container disposed radially outward relative to said axis of the main shaft, at least one solid electrode extending into said container and mounted for rotation with the latter about said eccentric axis to periodically extend into and be removed from the collected mercury, and an electrical circuit including the container, the mercury and the solid electrode arranged so that the mercury constitutes the cathode for the entire duration of each passage of current through the circuit with commutation taking place in the arc formed between said cathode and the electrode on opening of the circuit by withdrawal of the electrode from the collected mercury.

2. A. converter as set forth in claim i, wherein said eccentric axis is parallel to and spaced radially from the axis of said main shaft.

3, A converter as set forth in claim l, wherein said eccentric axis is arranged at right angles to the axis of said main shaft and intersects the latter axis.

4. A converter as set forth in claim 1, wherein said solid electrode acts as the anode in said circuit during the whole passage of the currentA therethrough.

5. A converter as set forth in claim 1, wherein said solid electrode has a channel formed therein at the portion of the electrode which is last withdrawn from the collected mercury so that said solid electrode acts as the anode in said circuit during the major part of each passage of current therethrough 1and mercury iiows from said channel during the withdrawal of said electrode from the collected mercury to form the anode during the instant of commutation.

6. A converter as set forth in claim l, wherein at least two circular conducting members are disposed concentric with said eccentric axis and mounted for rotation with said container about said eccentric axis, said circular conducting members being electrically connected tc the mercury in said container and to said solid electrode, respectively, and xed conducting tracks arranged with respect to said axis of the main shaft so that said circular conducting members effect continuous rolling contact with said tracks during movement of said container about said axis of the main shaft and said eccentric axis.

7. A converter as set forth in claim 6, wherein said eccentric yaxis is parallel to and spaced radially from the axis of said main shaft to describe a cylindrical body of revolution during its movement about said main shaft, and said xed conducting tracks are circular `and concentric with said axis of the main shaft to receive said circular conducting members against the inner surfaces of the related tracks so that said circular conducting members 'are centrifugally urged against said tracks by the movement of Said container 4and said conducting members about said axis of the main shaft.

8. A converter as set forth in claim 7, wherein said driving means is constructed and arranged to rotate said container and circular conducting members in the direction opposite to the rotation of said main shaft and at a speed providing a linear speed at the periphery of said circular conducting members equal to the linear speed of said periphery relative to said tracks resulting from the rotation of said main shaft so that said circular conducting members roll on said tracks without slipping.

9. A converter as set forth in claim 8, wherein said driving means includes epicyclie transmission means interposed between said main shaft and said container, said transmission means having a relatively fixed member, and means for adjusting the position of said fixed member to adjust the angular position of said container and solid electrode around said eccentric axis without displacing said eccentric axis relative to said `axis of the main shaft so that the timing of the commutation relative to the rotation of the main shaft may be varied.

HANS AESCHLIMANN.

REFERENCES CTED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 771,868 Freedman Oct. 11, 1904 973,525 Lucas Oct. 25, 1910 988,571 Hutton Apr. 4, 1911 1,031,893 Volk July 9, 1912 1,110,781 Hewitt Sept. 15, 1914 1,143,175 Cottrell et a1 June 15, 1915 1,412,228 Andersen etal Apr. 11, 1822 1,457,902 Gardeen June 5, 1923 FOREIGN PATENTS Number Country Date 573,204 Germany June 19, 1931 

